Patent document 1 describes an example of a known technique related to the above wireless microphone system.
Patent document 1 describes a communication device in which spread spectrum communication is performed between a base unit and a sub-unit using a spread code sequence serving as an encryption key. This improves interference and increases the privacy of signals. The spread code sequence used by the sub-unit is transmitted from the base unit to the sub-unit when the sub-unit is set in a setting area of the base unit with a terminal of the sub-unit in contact with a charge terminal of the base unit.